1. Field of the Invention
The present invention relates to an integrated circuit, and in particular, to a contact pad supporting structure of an integrated circuit.
2. Description of the Related Art
Power, grounding or input/output (I/O) connections for elements and devices of integrated circuits are provided by contact pads. Also, contact pads can be used for bonding or device testing of integrated circuits. However, as dimensions of integrated circuits shrink and density thereof increases, difficulty in providing efficient functioning and reliable contact pads have increased.
FIGS. 1A and 1B schematically show arrangements of via holes 110 of a conventional contact pad supporting structure 150. The conventional contact pad supporting structure 150 is disposed on a semiconductor substrate 100, wherein the conventional contact pad supporting structure 150 and the semiconductor substrate 100 are separated by an inter metal dielectric (IMD) layer 104. The conventional contact pad supporting structure 150 comprises a metal layer 106, an IMD layer 108, a contact pad metal layer 112 and a plurality of circular-shaped via plugs 110 through the IMD layer 108, wherein the metal layer 106 and the contact pad metal layer 112 are separated by the IMD layer 108, and wherein the via plugs 110 are electrically connected to the contact pad metal layer 112 and the metal layer 106. The circular-shaped via plugs 110 are periodically arranged. However, each of the via plugs 110 and the two via plugs on the opposite sides adjacent thereof have a same spacing. Also, the via plugs 110, substantially along one direction, are periodically arranged.
For the conventional contact pad supporting structure 150, deficiencies exist. Specifically, when a large bonding force or device testing stress is placed on the conventional contact pad supporting structure 150, a continuous cracking path 160 along the periodically arranged via plugs 110 of the dielectric layer 108 under the contact pad metal layer 112 may occur. The continuous cracking path 160 results in reduced reliability of the contact pads, thus, making it difficult to further decrease testing costs and reduce fabrication yields. Additionally, the conventional contact pad supporting structure 150 has weak mechanical strength, and thus, circuits are not able to be designed and disposed below the contact pad areas, hindering efficient use of space for integrated circuits.
Therefore, a contact pad supporting structure having better mechanical strength, and able to withstand a large bonding force or device testing stress is needed to further reduce device testing costs of integrated circuits and improve fabrication yields.